The present invention relates to twisting of yarn or threads and more particularly to twisting of at least two separate yarn or thread strands in accordance with selected patterns. The present invention also relates to carpets and textile substrates using twisted yarn.
In the art of twisting yarn and thread, hereinafter together referred to as yarn twisting, a pre-determined twist level and twist direction is selected and remains constant for a particular finished yarn. Twist level is defined as the turns of twist or wrap of the yarn or thread about each other for a given segment of length of the twisted yarn or thread. The twisting of yarn comprises twisting at least one strand or ply of yarn together or about another such that there is a pre-determined number of turns of yarn twisted with or wrapped about another yarn. Various twisting techniques are utilized in the art to obtain a twisted multiple ply yarn product. For example, ring twisting wherein strands of yarn pass through a ring and are twisted as the ring rotates about a rotating bobbin on which the yarn is wound; two-for-one twisting wherein two bobbins of yarn are combined within a common can, pass through the center of a rotating yarn twister spindle and out a radial hole; and cabling wherein one or more yarn strands enter the bottom of a rotating twister spindle at the center and exit through a radial hole and enters an eyelet or ring to form a balloon which throws out about a supply bobbin of another yarn with which it is twisted, are three such methods for twisting yarn strands together or one or more yarns twisted about another yarn. In each method it is the general practice to maintain the twist level or number of turns per inch of the yarn constant. Machines that perform these methods include a common drive motor, and the ratio between the yarn speed and the final yarn package speed, which determines the twist level, is obtained by the use of change twist gears. Thus, the twist level of a particular yarn is constant and is monitored to remain constant. In order to change twist level, different change twist gears are utilized, but this can only be done for one twisted yarn at a time, i.e., a single yarn has only one twist level.
It has been found that if the twist level of a given yarn may be varied along its length, products made from such yarn, such as carpet, may have unusual aesthetic styling. In the prior art, an attempt to obtain twist variation along the length of the yarn was proposed in Lloyd (U.S. Pat. No. 2,933,881), which utilizes a variable speed device wherein the output speed is controlled by a control lever either moved by a cam or manually moved to change the speed of the yarn take-up spool to vary the twist of the yarn within the final package. It clearly is impracticable to vary the twist manually with such an apparatus since reproducible results would not be obtainable. If a cam is used to create the twist level variation, the variation is limited by the shape and size of the cam, and if another pattern of twisting levels is desired, the cam must be changed.
Yamada et al. (U.S. Pat. No. 4,569,192) involves single strand spun yarns wherein the fibers are spun, drafted and twisted. It was proposed to vary the twist and drafting of the strand while the spun yarn strand is being formed in yarn spinning equipment.
However, there is no known proposal of a system for forming a twisted yarn having multiple plies of yarn which eliminates the need for changing gears, cams or other mechanical or manual devices, which employs fluid twisting or entanglement of the yarn, and which permits large twist pattern variations in the product such that the length of the segments of a desired twist level may be varied along with the twist level and/or the twist direction. Such yarn can be utilized for forming carpet or other textiles with unique and different patterns and aesthetics. Accordingly, it is desirable to provide a system whereby variations in yarn twist level and/or twist direction may be selectively made and wherein wide variations may be selected when twisting multiple strands of yarn together into a composite twisted yarn.